Carrier sense adaptive transmission (csat) in unlicensed spectrum

ABSTRACT

Systems and methods for Carrier Sense Adaptive Transmission (CSAT) and related operations in unlicensed spectrum are disclosed to reduce interference between co-existing Radio Access Technologies (RATs). The parameters for a given CSAT communication scheme may be adapted dynamically based on received signals from a transceiver for a native RAT to be protected and an identification of how that RAT is utilizing a shared resource such as an unlicensed band. Other operations such as Discontinuous Reception (DRX) may be aligned with a CSAT Time Division Multiplexed (TDM) communication pattern by way of a DRX broadcast/multicast message. Different TDM communication patterns may be staggered in time across different frequencies. Channel selection for a co-existing RAT may also be configured to afford further protection to native RATs by preferring operation on secondary channels as opposed to primary channels.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application for patent claims the benefit of U.S.Provisional Application No. 61/881,837, entitled “ADAPTING COMMUNICATIONBASED ON RESOURCE UTILIZATION,” filed Sep. 24, 2013, and U.S.Provisional Application No. 61/920,272, entitled “ADAPTING COMMUNICATIONBASED ON RESOURCE UTILIZATION,” filed Dec. 23, 2013, both assigned tothe assignee hereof, and expressly incorporated herein by reference intheir entirety.

REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT

The present application for patent is also related to the followingco-pending U.S. patent application: “CARRIER SENSE ADAPTIVE TRANSMISSION(CSAT) IN UNLICENSED SPECTRUM,” having Attorney Docket No. QC135183U2,filed concurrently herewith, assigned to the assignee hereof, andexpressly incorporated herein by reference in its entirety.

INTRODUCTION

Aspects of this disclosure relate generally to telecommunications, andmore particularly to co-existence between wireless Radio AccessTechnologies (RATs) and the like.

Wireless communication systems are widely deployed to provide varioustypes of communication content, such as voice, data, multimedia, and soon. Typical wireless communication systems are multiple-access systemscapable of supporting communication with multiple users by sharingavailable system resources (e.g., bandwidth, transmit power, etc.).Examples of such multiple-access systems include Code Division MultipleAccess (CDMA) systems, Time Division Multiple Access (TDMA) systems,Frequency Division Multiple Access (FDMA) systems, Orthogonal FrequencyDivision Multiple Access (OFDMA) systems, and others. These systems areoften deployed in conformity with specifications such as ThirdGeneration Partnership Project (3GPP), 3GPP Long Term Evolution (LTE),Ultra Mobile Broadband (UMB), Evolution Data Optimized (EV-DO),Institute of Electrical and Electronics Engineers (IEEE), etc.

In cellular networks, “macro cell” base stations provide connectivityand coverage to a large number of users over a certain geographicalarea. A macro network deployment is carefully planned, designed, andimplemented to offer good coverage over the geographical region. Evensuch careful planning, however, cannot fully accommodate channelcharacteristics such as fading, multipath, shadowing, etc., especiallyin indoor environments. Indoor users therefore often face coverageissues (e.g., call outages and quality degradation) resulting in pooruser experience.

To improve indoor or other specific geographic coverage, such as forresidential homes and office buildings, additional “small cell,”typically low-power base stations have recently begun to be deployed tosupplement conventional macro networks. Small cell base stations mayalso provide incremental capacity growth, richer user experience, and soon.

Recently, small cell LTE operations, for example, have been extendedinto the unlicensed frequency spectrum such as the Unlicensed NationalInformation Infrastructure (U-NII) band used by Wireless Local AreaNetwork (WLAN) technologies. This extension of small cell LTE operationis designed to increase spectral efficiency and hence capacity of theLTE system. However, it may also encroach on the operations of otherRATs that typically utilize the same unlicensed bands, most notably IEEE802.11x WLAN technologies generally referred to as “Wi-Fi.”

There therefore remains a need for improved co-existence for variousdevices operating in the increasingly crowded unlicensed frequencyspectrum.

SUMMARY

Systems and methods for Carrier Sense Adaptive Transmission (CSAT) andrelated operations in unlicensed spectrum are disclosed.

A method of CSAT for reducing interference between Radio AccessTechnologies (RATs) is disclosed. The method may comprise, for example:receiving signals via a resource, wherein a first transceiver operatingin accordance with a first RAT is used to receive the signals;identifying a utilization of the resource that is associated with thefirst RAT, wherein the identification is based on the received signals;setting one or more cycling parameters of a Time Division Multiplexing(TDM) communication pattern defining activated and deactivated periodsof transmission for a second RAT sharing the resource, wherein thesetting is based on the identified utilization of the resource; andcycling operation of the second RAT between activated and deactivatedperiods of transmission over the resource in accordance with the TDMcommunication pattern.

An apparatus for CSAT for reducing interference between RATs is alsodisclosed. The apparatus may comprise, for example, a transceiver, aprocessor, and memory coupled to the processor for storing related dataand instructions. The transceiver may be configured to, for example,receive signals via a resource, wherein the transceiver operates inaccordance with a first RAT to receive the signals. The processor may beconfigured to, for example: identify a utilization of the resource thatis associated with the first RAT, wherein the identification is based onthe received signals; set one or more cycling parameters of a TDMcommunication pattern defining activated and deactivated periods oftransmission for a second RAT sharing the resource, wherein the settingis based on the identified utilization of the resource; and controlcycling of operation of the second RAT between activated and deactivatedperiods of transmission over the resource in accordance with the TDMcommunication pattern.

Another method of coordinating Discontinuous Reception (DRX)configurations across user devices in a wireless communication system isalso disclosed. The method may comprise, for example: assigningdifferent DRX configurations for different communication channels;transmitting a DRX configuration message to a plurality of user devicesspecifying one or more DRX parameters for each of the different DRXconfigurations; and communicating via the communication channels,wherein for each of the communication channels, the communication uses acorresponding one of the DRX configurations.

Another apparatus for coordinating DRX configurations across userdevices in a wireless communication system is also disclosed. Theapparatus may comprise, for example, a transceiver, a processor, andmemory coupled to the processor for storing related data andinstructions. The processor may be configured to, for example, assigndifferent DRX configurations for different communication channels. Thetransceiver may be configured to, for example: transmit a DRXconfiguration message to a plurality of user devices specifying one ormore DRX parameters for each of the different DRX configurations; andcommunicate via the communication channels, wherein for each of thecommunication channels, the communication uses a corresponding one ofthe DRX configurations.

Another method of CSAT for reducing interference between RATs is alsodisclosed. The method may comprise, for example: receiving signals via aresource, wherein a first RAT is used to receive the signals;identifying a utilization of the resource that is associated with thefirst RAT, wherein the identification is based on the received signals;setting one or more cycling parameters of a first TDM communicationpattern defining activated and deactivated periods of transmission on afirst frequency for a second RAT sharing the resource, wherein thesetting is based on the identified utilization of the resource; settingone or more cycling parameters of a second TDM communication patterndefining activated and deactivated periods of transmission on a secondfrequency for the second RAT, wherein the setting is based on theidentified utilization of the resource, and wherein the first TDMcommunication pattern and the second TDM communication pattern arestaggered in time with respect to an overlap in their activated anddeactivated periods; and cycling operation of the second RAT betweenactivated and deactivated periods of transmission over the resource onthe first and second frequencies in accordance with the first and secondTDM communication patterns.

Another apparatus for CSAT for reducing interference between RATs isalso disclosed. The apparatus may comprise, for example, a transceiver,a processor, and memory coupled to the processor for storing relateddata and instructions. The transceiver may be configured to, forexample, receive signals via a resource, wherein the first transceiveroperates in accordance with a first RAT to receive the signals. Theprocessor may be configured to, for example: identify a utilization ofthe resource that is associated with the first RAT, wherein theidentification is based on the received signals; set one or more cyclingparameters of a first TDM communication pattern defining activated anddeactivated periods of transmission on a first frequency for a secondRAT sharing the resource, wherein the setting is based on the identifiedutilization of the resource; set one or more cycling parameters of asecond TDM communication pattern defining activated and deactivatedperiods of transmission on a second frequency for the second RAT,wherein the setting is based on the identified utilization of theresource, and wherein the first TDM communication pattern and the secondTDM communication pattern are staggered in time with respect to anoverlap in their activated and deactivated periods; and control cyclingof operation of the second RAT between activated and deactivated periodsof transmission over the resource on the first and second frequencies inaccordance with the first and second TDM communication patterns.

Another method of channel selection among a plurality of frequencies forreducing interference between RATs is also disclosed. The method maycomprise, for example: receiving signals via a resource, wherein a firstRAT is used to receive the signals; identifying a utilization of theresource that is associated with the first RAT, wherein theidentification is based on the received signals; selecting a firstfrequency from the plurality of frequencies for communication over theresource by a second RAT in response to the identified utilization ofthe resource being below a clean channel threshold on the firstfrequency; and selecting a second frequency from the plurality offrequencies for communication over the resource by the second RAT inresponse to the identified utilization of the resource being above theclean channel threshold on each of the plurality of frequencies, whereina frequency associated with a secondary channel of the first RAT isselected as the second frequency if one or more secondary channels areidentified as operating on the resource, and wherein a frequencyassociated with a primary channel of the first RAT is selected as thesecond frequency if no secondary channels are identified as operating onthe resource.

Another apparatus for channel selection among a plurality of frequenciesfor reducing interference between RATs is also disclosed. The apparatusmay comprise, for example, a transceiver, a processor, and memorycoupled to the processor for storing related data and instructions. Thetransceiver may be configured to, for example, receive signals via aresource, wherein the first transceiver operates in accordance with afirst RAT to receive the signals. The processor may be configured to,for example: identify a utilization of the resource that is associatedwith the first RAT, wherein the identification is based on the receivedsignals; select a first frequency from the plurality of frequencies forcommunication over the resource by a second RAT in response to theidentified utilization of the resource being below a clean channelthreshold on the first frequency; and select a second frequency from theplurality of frequencies for communication over the resource by thesecond RAT in response to the identified utilization of the resourcebeing above the clean channel threshold on each of the plurality offrequencies, wherein a frequency associated with a secondary channel ofthe first RAT is selected as the second frequency if one or moresecondary channels are identified as operating on the resource, andwherein a frequency associated with a primary channel of the first RATis selected as the second frequency if no secondary channels areidentified as operating on the resource.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the disclosure and are provided solely forillustration of the aspects and not limitation thereof

FIG. 1 illustrates an example mixed-deployment wireless communicationsystem including macro cell base stations and small cell base stations.

FIG. 2 is a block diagram illustrating an example downlink framestructure for LTE communications.

FIG. 3 is a block diagram illustrating an example uplink frame structurefor LTE communications.

FIG. 4 illustrates an example small cell base station with co-locatedradio components (e.g., LTE and Wi-Fi) configured for unlicensedspectrum operation.

FIG. 5 is a signaling flow diagram illustrating an example messageexchange between co-located radios.

FIG. 6 is a system-level co-existence state diagram illustratingdifferent aspects of cellular operation that may be specially adapted tomanage co-existence between different Radio Access Technologies (RATs)operating on a shared unlicensed band.

FIG. 7 illustrates in more detail certain aspects a Carrier SenseAdaptive Transmission (CSAT) communication scheme for cycling cellularoperation in accordance with a long-term Time Division Multiplexed (TDM)communication pattern.

FIG. 8 is a flow diagram illustrating an example method of CSATparameter adaptation for reducing interference between RATs.

FIG. 9 illustrates an example opportunistic modification of a CSATcommunication scheme to accommodate pending retransmissions.

FIG. 10 illustrates an example of inter-RAT coordination utilizing aClear-to-Send-to-Self (CTS2S) message.

FIGS. 11-12 are signaling flow diagrams illustrating different examplesof split processing and message exchanges between a small cell basestation and a user device for coordinating CSAT operation.

FIG. 13 illustrates an example Discontinuous Reception (DRX)communication mode.

FIG. 14 illustrates an example DRX broadcast/multicast message forconfiguring user devices in accordance with various DRX parameters.

FIG. 15 is a flow diagram illustrating an example method of coordinatingDRX configurations across user devices in a wireless communicationsystem.

FIG. 16 illustrates an example CSAT communication scheme utilizingstaggered TDM communication patterns across different frequencies.

FIG. 17 illustrates another example CSAT communication scheme utilizingstaggered TDM communication patterns across different frequencies.

FIG. 18 is a flow diagram illustrating an example method of CSATcommunication employing staggered TDM communication patterns.

FIG. 19 is a flow diagram illustrating an example method of channelselection among a plurality of channels.

FIG. 20 is a simplified block diagram of several sample aspects ofcomponents that may be employed in communication nodes and configured tosupport communication as taught herein.

FIGS. 21-24 are other simplified block diagrams of several sampleaspects of apparatuses configured to support communication as taughtherein.

FIG. 25 illustrates an example communication system environment in whichthe teachings and structures herein may be may be incorporated.

DETAILED DESCRIPTION

The present disclosure relates generally to Carrier Sense AdaptiveTransmission (CSAT) communication and various related aspects to reduceinterference between co-existing Radio Access Technologies (RATs). Theparameters for a given CSAT communication scheme may be adapteddynamically based on received signals for a native RAT to be protectedand an identification of how that RAT is utilizing a shared resourcesuch as an unlicensed band. To better associate received signaling withthe native RAT and distinguish it from other RAT signaling as well asnoise, a particular transceiver operating in accordance with the nativeRAT may be used to receive the signals (rather than a transceiveroperating in accordance with another RAT that scans for aggregatebackground signal strength). For example, for a shared Wi-Fi medium, aco-located Wi-Fi radio may sniff the medium for Wi-Fi packets. Wi-Fipackets may be detected by decoding one or more Wi-Fi signatures andutilization of the Wi-Fi medium may be determined based on the extracted(e.g., decoded) characteristics of the of the detected Wi-Fi packets.Various CSAT cycling parameters defining a corresponding Time DivisionMultiplexed (TDM) communication pattern may be set or changed as desiredbased on the identified utilization, such as a duty cycle, a transmitpower, cycle timing (e.g., the start/stop time of each CSAT cycle), andso on.

It may be advantageous to align other operations such as DiscontinuousReception (DRX) with the CSAT TDM communication pattern. A DRXbroadcast/multicast message is provided for configuring user devices inaccordance with various DRX parameters, as an alternative to other(unicast) Radio Resource Control (RRC) signaling. By utilizing such abroadcast/multicast message, a base station may establish different CSATTDM communication patterns on different frequencies while at the sametime configuring DRX to align with each of the different CSAT TDMcommunication patterns.

The TDM communication patterns may also be staggered in time across thedifferent frequencies with respect to an overlap in their CSAT ON(activated)/CSAT OFF (deactivated) periods, such that user traffic on aparticular frequency that is deactivated for a given period may beswitched over to another, activated frequency for service during thattime. The staggering of TDM communication patterns may be employedacross different frequencies for downlink CSAT communication (e.g.,transmission by the small cell base station) as well as for uplink CSATcommunication (e.g., transmission by a user device).

Channel selection for a co-existing RAT may also be configured to affordfurther protection to native RATs such as Wi-Fi by preferring operationon secondary channels as opposed to primary channels (if no cleanchannel is found). In either case, whether a primary or secondarychannel is selected, a CSAT communication scheme may be implemented onthe selected channel in accordance with the techniques provided hereinto afford additional protection to the native RAT.

More specific aspects of the disclosure are provided in the followingdescription and related drawings directed to various examples providedfor illustration purposes. Alternate aspects may be devised withoutdeparting from the scope of the disclosure. Additionally, well-knownaspects of the disclosure may not be described in detail or may beomitted so as not to obscure more relevant details.

Those of skill in the art will appreciate that the information andsignals described below may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the description below may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof, depending inpart on the particular application, in part on the desired design, inpart on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., Application Specific Integrated Circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. In addition, for each of theaspects described herein, the corresponding form of any such aspect maybe implemented as, for example, “logic configured to” perform thedescribed action.

FIG. 1 illustrates an example mixed-deployment wireless communicationsystem, in which small cell base stations are deployed in conjunctionwith and to supplement the coverage of macro cell base stations. As usedherein, small cells generally refer to a class of low-powered basestations that may include or be otherwise referred to as femto cells,pico cells, micro cells, etc. As noted in the background above, they maybe deployed to provide improved signaling, incremental capacity growth,richer user experience, and so on.

The illustrated wireless communication system 100 is a multiple-accesssystem that is divided into a plurality of cells 102 and configured tosupport communication for a number of users. Communication coverage ineach of the cells 102 is provided by a corresponding base station 110,which interacts with one or more user devices 120 via DownLink (DL)and/or UpLink (UL) connections. In general, the DL corresponds tocommunication from a base station to a user device, while the ULcorresponds to communication from a user device to a base station.

As will be described in more detail below, these different entities maybe variously configured in accordance with the teachings herein toprovide or otherwise support the CSAT and related operations discussedbriefly above. For example, one or more of the small cell base stations110 may include a CSAT management module 112, while one or more of theuser devices 120 may include a CSAT management module 122.

As used herein, the terms “user device” and “base station” are notintended to be specific or otherwise limited to any particular RadioAccess Technology (RAT), unless otherwise noted. In general, such userdevices may be any wireless communication device (e.g., a mobile phone,router, personal computer, server, etc.) used by a user to communicateover a communications network, and may be alternatively referred to indifferent RAT environments as an Access Terminal (AT), a Mobile Station(MS), a Subscriber Station (STA), a User Equipment (UE), etc. Similarly,a base station may operate according to one of several RATs incommunication with user devices depending on the network in which it isdeployed, and may be alternatively referred to as an Access Point (AP),a Network Node, a NodeB, an evolved NodeB (eNB), etc. In addition, insome systems a base station may provide purely edge node signalingfunctions while in other systems it may provide additional controland/or network management functions.

Returning to FIG. 1, the different base stations 110 include an examplemacro cell base station 110A and two example small cell base stations110B, 110C. The macro cell base station 110A is configured to providecommunication coverage within a macro cell coverage area 102A, which maycover a few blocks within a neighborhood or several square miles in arural environment. Meanwhile, the small cell base stations 110B, 110Care configured to provide communication coverage within respective smallcell coverage areas 102B, 102C, with varying degrees of overlap existingamong the different coverage areas. In some systems, each cell may befurther divided into one or more sectors (not shown).

Turning to the illustrated connections in more detail, the user device120A may transmit and receive messages via a wireless link with themacro cell base station 110A, the message including information relatedto various types of communication (e.g., voice, data, multimediaservices, associated control signaling, etc.). The user device 120B maysimilarly communicate with the small cell base station 110B via anotherwireless link, and the user device 120C may similarly communicate withthe small cell base station 110C via another wireless link. In addition,in some scenarios, the user device 120C, for example, may alsocommunicate with the macro cell base station 110A via a separatewireless link in addition to the wireless link it maintains with thesmall cell base station 110C.

As is further illustrated in FIG. 1, the macro cell base station 110Amay communicate with a corresponding wide area or external network 130,via a wired link or via a wireless link, while the small cell basestations 110B, 110C may also similarly communicate with the network 130,via their own wired or wireless links. For example, the small cell basestations 110B, 110C may communicate with the network 130 by way of anInternet Protocol (IP) connection, such as via a Digital Subscriber Line(DSL, e.g., including Asymmetric DSL (ADSL), High Data Rate DSL (HDSL),Very High Speed DSL (VDSL), etc.), a TV cable carrying IP traffic, aBroadband over Power Line (BPL) connection, an Optical Fiber (OF) cable,a satellite link, or some other link.

The network 130 may comprise any type of electronically connected groupof computers and/or devices, including, for example, Internet, Intranet,Local Area Networks (LANs), or Wide Area Networks (WANs). In addition,the connectivity to the network may be, for example, by remote modem,Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), Fiber DistributedDatalink Interface (FDDI) Asynchronous Transfer Mode (ATM), WirelessEthernet (IEEE 802.11), Bluetooth (IEEE 802.15.1), or some otherconnection. As used herein, the network 130 includes network variationssuch as the public Internet, a private network within the Internet, asecure network within the Internet, a private network, a public network,a value-added network, an intranet, and the like. In certain systems,the network 130 may also comprise a Virtual Private Network (VPN).

Accordingly, it will be appreciated that the macro cell base station110A and/or either or both of the small cell base stations 110B, 110Cmay be connected to the network 130 using any of a multitude of devicesor methods. These connections may be referred to as the “backbone” orthe “backhaul” of the network, and may in some implementations be usedto manage and coordinate communications between the macro cell basestation 110A, the small cell base station 110B, and/or the small cellbase station 110C. In this way, as a user device moves through such amixed communication network environment that provides both macro celland small cell coverage, the user device may be served in certainlocations by macro cell base stations, at other locations by small cellbase stations, and, in some scenarios, by both macro cell and small cellbase stations.

For their wireless air interfaces, each base station 110 may operateaccording to one of several RATs depending on the network in which it isdeployed. These networks may include, for example, Code DivisionMultiple Access (CDMA) networks, Time Division Multiple Access (TDMA)networks, Frequency Division Multiple Access (FDMA) networks, OrthogonalFDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, and soon. The terms “network” and “system” are often used interchangeably. ACDMA network may implement a RAT such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a RAT such as Global System forMobile Communications (GSM). An OFDMA network may implement a RAT suchas Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20,Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of Universal MobileTelecommunication System (UMTS). Long Term Evolution (LTE) is a releaseof UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are describedin documents from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 is described in documents from an organizationnamed “3rd Generation Partnership Project 2” (3GPP2). These documentsare publicly available.

For illustration purposes, an example downlink and uplink framestructure for an LTE signaling scheme is described below with referenceto FIGS. 2-3.

FIG. 2 is a block diagram illustrating an example downlink framestructure for LTE communications. In LTE, the base stations 110 of FIG.1 are generally referred to as eNBs and the user devices 120 aregenerally referred to as UEs. The transmission timeline for the downlinkmay be partitioned into units of radio frames. Each radio frame may havea predetermined duration (e.g., 10 milliseconds (ms)) and may bepartitioned into 10 subframes with indices of 0 through 9. Each subframemay include two slots. Each radio frame may thus include 20 slots withindices of 0 through 19. Each slot may include L symbol periods, e.g., 7symbol periods for a normal cyclic prefix (as shown in FIG. 2) or 6symbol periods for an extended cyclic prefix. The 2L symbol periods ineach subframe may be assigned indices of 0 through 2L−1. The availabletime frequency resources may be partitioned into resource blocks. Eachresource block may cover N subcarriers (e.g., 12 subcarriers) in oneslot.

In LTE, an eNB may send a Primary Synchronization Signal (PSS) and aSecondary Synchronization Signal (SSS) for each cell in the eNB. The PSSand SSS may be sent in symbol periods 5 and 6, respectively, in each ofsubframes 0 and 5 of each radio frame with the normal cyclic prefix, asshown in FIG. 2. The synchronization signals may be used by UEs for celldetection and acquisition. The eNB may send a Physical Broadcast Channel(PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH maycarry certain system information.

Reference signals are transmitted during the first and fifth symbolperiods of each slot when the normal cyclic prefix is used and duringthe first and fourth symbol periods when the extended cyclic prefix isused. For example, the eNB may send a Cell-specific Reference Signal(CRS) for each cell in the eNB on all component carriers. The CRS may besent in symbols 0 and 4 of each slot in case of the normal cyclicprefix, and in symbols 0 and 3 of each slot in case of the extendedcyclic prefix. The CRS may be used by UEs for coherent demodulation ofphysical channels, timing and frequency tracking, Radio Link Monitoring(RLM), Reference Signal Received Power (RSRP), and Reference SignalReceived Quality (RSRQ) measurements, etc.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) inthe first symbol period of each subframe, as seen in FIG. 2. The PCFICHmay convey the number of symbol periods (M) used for control channels,where M may be equal to 1, 2, or 3 and may change from subframe tosubframe. M may also be equal to 4 for a small system bandwidth, e.g.,with less than 10 resource blocks. In the example shown in FIG. 2, M=3.The eNB may send a Physical HARQ Indicator Channel (PHICH) and aPhysical Downlink Control Channel (PDCCH) in the first M symbol periodsof each subframe. The PDCCH and PHICH are also included in the firstthree symbol periods in the example shown in FIG. 2. The PHICH may carryinformation to support Hybrid Automatic Repeat Request (HARQ). The PDCCHmay carry information on resource allocation for UEs and controlinformation for downlink channels. The eNB may send a Physical DownlinkShared Channel (PDSCH) in the remaining symbol periods of each subframe.The PDSCH may carry data for UEs scheduled for data transmission on thedownlink. The various signals and channels in LTE are described in 3GPPTS 36.211, entitled “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation,” which is publiclyavailable.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNB. The eNB may send the PCFICH and PHICHacross the entire system bandwidth in each symbol period in which thesechannels are sent. The eNB may send the PDCCH to groups of UEs incertain portions of the system bandwidth. The eNB may send the PDSCH tospecific UEs in specific portions of the system bandwidth. The eNB maysend the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to allUEs, may send the PDCCH in a unicast manner to specific UEs, and mayalso send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element may cover one subcarrier in one symbol period andmay be used to send one modulation symbol, which may be a real orcomplex value. Resource elements not used for a reference signal in eachsymbol period may be arranged into Resource Element Groups (REGs). EachREG may include four resource elements in one symbol period. The PCFICHmay occupy four REGs, which may be spaced approximately equally acrossfrequency, in symbol period 0. The PHICH may occupy three REGs, whichmay be spread across frequency, in one or more configurable symbolperiods. For example, the three REGs for the PHICH may all belong insymbol period 0 or may be spread in symbol periods 0, 1, and 2. ThePDCCH may occupy 9, 18, 32, or 64 REGs, which may be selected from theavailable REGs, in the first M symbol periods. Only certain combinationsof REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for the PDCCH. An eNB may send the PDCCH to the UE in anyof the combinations that the UE will search.

FIG. 3 is a block diagram illustrating an example uplink frame structurefor LTE communications. The available resource blocks (which may bereferred to as RBs) for the UL may be partitioned into a data sectionand a control section. The control section may be formed at the twoedges of the system bandwidth and may have a configurable size. Theresource blocks in the control section may be assigned to UEs fortransmission of control information. The data section may include allresource blocks not included in the control section. The design in FIG.3 results in the data section including contiguous subcarriers, whichmay allow a single UE to be assigned all of the contiguous subcarriersin the data section.

A UE may be assigned resource blocks in the control section to transmitcontrol information to an eNB. The UE may also be assigned resourceblocks in the data section to transmit data to the eNB. The UE maytransmit control information in a Physical Uplink Control Channel(PUCCH) on the assigned resource blocks in the control section. The UEmay transmit only data or both data and control information in aPhysical Uplink Shared Channel (PUSCH) on the assigned resource blocksin the data section. An uplink transmission may span both slots of asubframe and may hop across frequency as shown in FIG. 3.

Returning to FIG. 1, cellular systems such as LTE are typically confinedto one or more licensed frequency bands that have been reserved for suchcommunications (e.g., by a government entity such as the FederalCommunications Commission (FCC) in the United States). However, certaincommunication systems, in particular those employing small cell basestations as in the design of FIG. 1, have extended cellular operationsinto unlicensed frequency bands such as the Unlicensed NationalInformation Infrastructure (U-NII) band used by Wireless Local AreaNetwork (WLAN) technologies. For illustration purposes, the descriptionbelow may refer in some respects to an LTE system operating on anunlicensed band by way of example when appropriate, although it will beappreciated that such descriptions are not intended to exclude othercellular communication technologies. LTE on an unlicensed band may alsobe referred to herein as LTE/LTE-Advanced in unlicensed spectrum, orsimply LTE in the surrounding context. With reference to FIGS. 2-3above, the PSS, SSS, CRS, PBCH, PUCCH, and PUSCH in LTE on an unlicensedband are otherwise the same or substantially the same as in the LTEstandard described in 3GPP TS 36.211, entitled “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation,”which is publicly available.

The unlicensed spectrum may be employed by cellular systems in differentways. For example, in some systems, the unlicensed spectrum may beemployed in a standalone configuration, with all carriers operatingexclusively in an unlicensed portion of the wireless spectrum (e.g., LTEStandalone). In other systems, the unlicensed spectrum may be employedin a manner that is supplemental to licensed band operation by utilizingone or more unlicensed carriers operating in the unlicensed portion ofthe wireless spectrum in conjunction with an anchor licensed carrieroperating in the licensed portion of the wireless spectrum (e.g., LTESupplemental DownLink (SDL)). In either case, carrier aggregation may beemployed to manage the different component carriers, with one carrierserving as the Primary Cell (PCell) for the corresponding user (e.g., ananchor licensed carrier in LTE SDL or a designated one of the unlicensedcarriers in LTE Standalone) and the remaining carriers serving asrespective Secondary Cells (SCells). In this way, the PCell may providea Frequency Division Duplexed (FDD) pair of downlink and uplink carriers(licensed or unlicensed), with each SCell providing additional downlinkcapacity as desired.

The extension of small cell operation into unlicensed frequency bandssuch as the U-NII (5 GHz) band may therefore be implemented in a varietyof ways and increase the capacity of cellular systems such as LTE. Asdiscussed briefly in the background above, however, it may also encroachon the operations of other “native” RATs that typically utilize the sameunlicensed band, most notably IEEE 802.11x WLAN technologies generallyreferred to as “Wi-Fi.”

In some small cell base station designs, the small cell base station mayinclude such a native RAT radio co-located with its cellular radio.According to various aspects described herein, the small cell basestation may leverage the co-located radio to facilitate co-existencebetween the different RATs when operating on a shared unlicensed band.For example, the co-located radio may be used to conduct differentmeasurements on the unlicensed band and dynamically determine the extentto which the unlicensed band is being utilized by devices operating inaccordance with the native RAT. The cellular radio's use of the sharedunlicensed band may then be specially adapted to balance the desire forefficient cellular operation against the need for stable co-existence.

FIG. 4 illustrates an example small cell base station with co-locatedradio components configured for unlicensed spectrum operation. The smallcell base station 400 may correspond, for example, to one of the smallcell base stations 110B, 110C illustrated in FIG. 1. In this example,the small cell base station 400 is configured to provide a WLAN airinterface (e.g., in accordance with an IEEE 802.11x protocol) inaddition to a cellular air interface (e.g., in accordance with an LTEprotocol). For illustration purposes, the small cell base station 400 isshown as including an 802.11x radio component/module (e.g., transceiver)402 co-located with an LTE radio component/module (e.g., transceiver)404.

As used herein, the term co-located (e.g., radios, base stations,transceivers, etc.) may include in accordance with various aspects, oneor more of, for example: components that are in the same housing;components that are hosted by the same processor; components that arewithin a defined distance of one another; and/or components that areconnected via an interface (e.g., an Ethernet switch) where theinterface meets the latency requirements of any required inter-componentcommunication (e.g., messaging). In some designs, the advantagesdiscussed herein may be achieved by adding a radio component of thenative unlicensed band RAT of interest to a given cellular small cellbase station without that base station necessarily providingcorresponding communication access via the native unlicensed band RAT(e.g., adding a Wi-Fi chip or similar circuitry to an LTE small cellbase station). If desired, a low functionality Wi-Fi circuit may beemployed to reduce costs (e.g., a Wi-Fi receiver simply providinglow-level sniffing).

Returning to FIG. 4, the Wi-Fi radio 402 and the LTE radio 404 mayperform monitoring of one or more channels (e.g., on a correspondingcarrier frequency) to perform various corresponding operating channel orenvironment measurements (e.g., CQI, RSSI, RSRP, or other RLMmeasurements) using corresponding Network/Neighbor Listen (NL) modules406 and 408, respectively, or any other suitable component(s).

The small cell base station 400 may communicate with one or more userdevices via the Wi-Fi radio 402 and the LTE radio 404, illustrated as anSTA 450 and a UE 460, respectively. Similar to the Wi-Fi radio 402 andthe LTE radio 404, the STA 450 includes a corresponding NL module 452and the UE 460 includes a corresponding NL module 462 for performingvarious operating channel or environment measurements, eitherindependently or under the direction of the Wi-Fi radio 402 and the LTEradio 404, respectively. In this regard, the measurements may beretained at the STA 450 and/or the UE 460, or reported to the Wi-Firadio 402 and the LTE radio 404, respectively, with or without anypre-processing being performed by the STA 450 or the UE 460.

While FIG. 4 shows a single STA 450 and a single UE 460 for illustrationpurposes, it will be appreciated that the small cell base station 400can communicate with multiple STAs and/or UEs. Additionally, while FIG.4 illustrates one type of user device communicating with the small cellbase station 400 via the Wi-Fi radio 402 (i.e., the STA 450) and anothertype of user device communicating with the small cell base station 400via the LTE radio 404 (i.e., the UE 460), it will be appreciated that asingle user device (e.g., a smartphone) may be capable of communicatingwith the small cell base station 400 via both the Wi-Fi radio 402 andthe LTE radio 404, either simultaneously or at different times.

As is further illustrated in FIG. 4, the small cell base station 400 mayalso include a network interface 410, which may include variouscomponents for interfacing with corresponding network entities (e.g.,Self-Organizing Network (SON) nodes), such as a component forinterfacing with a Wi-Fi SON 412 and/or a component for interfacing withan LTE SON 414. The small cell base station 400 may also include a host420, which may include one or more general purpose controllers orprocessors 422 and memory 424 configured to store related data and/orinstructions. The host 420 may perform processing in accordance with theappropriate RAT(s) used for communication (e.g., via a Wi-Fi protocolstack 426 and/or an LTE protocol stack 428), as well as other functionsfor the small cell base station 400. In particular, the host 420 mayfurther include a RAT interface 430 (e.g., a bus or the like) thatenables the radios 402 and 404 to communicate with one another viavarious message exchanges.

FIG. 5 is a signaling flow diagram illustrating an example messageexchange between co-located radios. In this example, one RAT (e.g., LTE)requests a measurement from another RAT (e.g., Wi-Fi) andopportunistically ceases transmission for the measurement. FIG. 5 willbe explained below with continued reference to FIG. 4.

Initially, the LTE SON 414 notifies the LTE stack 428 via a message 520that a measurement gap is upcoming on the shared unlicensed band. TheLTE SON 414 then sends a command 522 to cause the LTE radio (RF) 404 totemporarily turn off transmission on the unlicensed band, in response towhich the LTE radio 404 disables the appropriate RF components for aperiod of time (e.g., so as to not interfere with any measurementsduring this time).

The LTE SON 414 also sends a message 524 to the co-located Wi-Fi SON 412requesting that a measurement be taken on the unlicensed band. Inresponse, the Wi-Fi SON 412 sends a corresponding request 526 via theWi-Fi stack 426 to the Wi-Fi radio 402, or some other suitable Wi-Firadio component (e.g., a low cost, reduced functionality Wi-Fireceiver).

After the Wi-Fi radio 402 conducts measurements for Wi-Fi relatedsignaling on the unlicensed band, a report 528 including the results ofthe measurements is sent to the LTE SON 414 via the Wi-Fi stack 426 andthe Wi-Fi SON 412. In some instances, the measurement report may includenot only measurements performed by the Wi-Fi radio 402 itself, but alsomeasurements collected by the Wi-Fi radio 402 from the STA 450. The LTESON 414 may then send a command 530 to cause the LTE radio 404 to turnback on transmission on the unlicensed band (e.g., at the end of thedefined period of time).

The information included in the measurement report (e.g., informationindicative of how Wi-Fi devices are utilizing the unlicensed band) maybe compiled along with various LTE measurements and measurement reports.Based on information about the current operating conditions on theshared unlicensed band (e.g., as collected by one or a combination ofthe Wi-Fi radio 402, the LTE radio 404, the STA 450, and/or the UE 460),the small cell base station 400 may specially adapt different aspects ofits cellular operations in order to manage co-existence between thedifferent RATs. Returning to FIG. 5, the LTE SON 414, for example, maythen send a message 532 that informs the LTE stack 428 how LTEcommunication is to be modified.

There are several aspects of cellular operation that may be adapted inorder to manage co-existence between the different RATs. For example,the small cell base station 400 may select certain carriers aspreferable when operating in the unlicensed band, may opportunisticallyenable or disable operation on those carriers, may selectively adjustthe transmission power of those carriers, if necessary (e.g.,periodically or intermittently in accordance with a transmissionpattern), and/or take other steps to balance the desire for efficientcellular operation against the need for stable co-existence.

FIG. 6 is a system-level co-existence state diagram illustratingdifferent aspects of cellular operation that may be specially adapted tomanage co-existence between different RATs operating on a sharedunlicensed band. As shown, the techniques in this example includeoperations that will be referred to herein as Channel Selection (CHS)where appropriate unlicensed carriers are analyzed, OpportunisticSupplemental Downlink (OSDL) where operation on one or morecorresponding SCells is configured or deconfigured, and Carrier SenseAdaptive Transmission (CSAT) where the transmission power on thoseSCells is adapted, if necessary, by cycling between periods of hightransmission power (e.g., an ON state, as a special case) and lowtransmission power (e.g., an OFF state, as a special case).

For CHS (block 610), a channel selection algorithm may perform certainperiodic or event-driven scanning procedures (e.g., initial or thresholdtriggered) (block 612). With reference to FIG. 4, the scanningprocedures may utilize, for example, one or a combination of the Wi-Firadio 402, the LTE radio 404, the STA 450, and/or the UE 460. The scanresults may be stored (e.g., over a sliding time window) in acorresponding database (block 614) and used to classify the differentchannels in terms of their potential for cellular operation (block 616).For example, a given channel may be classified, at least in part, basedon whether it is a clean channel or whether it will need to be affordedsome level of protection for co-channel communications. Various costfunctions and associated metrics may be employed in the classificationand related calculations.

If a clean channel is identified (‘yes’ at decision 618), acorresponding SCell may be operated without concern for impactingco-channel communications (state 619). On the other hand, if no cleanchannel is identified, further processing may be utilized to reduce theimpact on co-channel communications (‘no’ at decision 618), as describedbelow.

Turning to OSDL (block 620), input may be received from the channelselection algorithm as well as from other sources, such as variousmeasurements, schedulers, traffic buffers, etc. (block 622), todetermine whether unlicensed operation is warranted without a cleanchannel being available (decision 624). For example, if there is notenough traffic to support a secondary carrier in the unlicensed band(‘no’ at decision 624), the corresponding SCell that supports it may bedisabled (state 626). Conversely, if there is a substantial amount oftraffic (‘yes’ at decision 624), even though a clean channel is notavailable, an SCell may nevertheless be constructed from one or more ofthe remaining carriers by invoking CSAT operation (block 630) tomitigate the potential impact on co-existence.

Returning to FIG. 6, the SCell may be initially enabled in adeconfigured state (state 628). The SCell along with one or morecorresponding user devices may then be configured and activated (state630) for normal operation. In LTE, for example, an associated UE may beconfigured and deconfigured via corresponding RRC Config/Deconfigmessages to add the SCell to its active set. Activation and deactivationof the associated UE may be performed, for example, by using MediumAccess Control (MAC) Control Element (CE) Activation/Deactivationcommands. At a later time, when the traffic level drops below athreshold, for example, an RRC Deconfig message may be used to removethe SCell from the UE's active set, and return the system to thedeconfigured state (state 628). If all UEs are deconfigured, OSDL may beinvoked to turn the SCell off.

During CSAT operation (block 630), the SCell may remain configured butbe cycled between periods of activated operation (state 632) and periodsof deactivated operation (state 634) in accordance with a (long-term)Time Division Multiplexed (TDM) communication pattern. In theconfigured/activated state (state 632), the SCell may operate atrelatively high power (e.g., full powered ON state). In theconfigured/deactivated state (state 634), the SCell may operate at areduced, relatively low power (e.g., depowered OFF state).

FIG. 7 illustrates in more detail certain aspects a CSAT communicationscheme for cycling cellular operation in accordance with a long-term TDMcommunication pattern. As discussed above in relation to FIG. 6, CSATmay be selectively enabled on one or more SCells as appropriate tofacilitate co-existence in unlicensed spectrum, even when a cleanchannel free of competing RAT operation is not available.

When enabled, SCell operation is cycled between CSAT ON (activated)periods and CSAT OFF (deactivated) periods within a given CSAT cycle(T_(CSAT)). One or more associated user devices may be similarly cycledbetween corresponding MAC activated and MAC deactivated periods. Duringan associated activated period of time T_(ON), SCell transmission on theunlicensed band may proceed at a normal, relatively high transmissionpower. During an associated deactivated period of time T_(OFF), however,the SCell remains in a configured state but transmission on theunlicensed band is reduced or even fully disabled to yield the medium toa competing RAT (as well as to perform various measurements via aco-located radio of the competing RAT).

Each of the associated CSAT parameters, including, for example, the CSATpattern duty cycle (i.e., T_(ON)/T_(CSAT)), cycle timing (e.g., thestart/stop time of each CSAT cycle), and the relative transmissionpowers during activated/deactivated periods, may be adapted based on thecurrent signaling conditions to optimize CSAT operation. As an example,if the utilization of a given channel by Wi-Fi devices is high, an LTEradio may adjust one or more of the CSAT parameters such that usage ofthe channel by the LTE radio is reduced. For example, the LTE radio mayreduce its transmit duty cycle or transmit power on the channel.Conversely, if utilization of a given channel by Wi-Fi devices is low,an LTE radio may adjust one or more of the CSAT parameters such thatusage of the channel by the LTE radio is increased. For example, the LTEradio may increase its transmit duty cycle or transmit power on thechannel. In either case, the CSAT ON (activated) periods may be madesufficiently long (e.g., greater than or equal to about 200 msec) toprovide user devices with a sufficient opportunity to perform at leastone measurement during each CSAT ON (activated) period.

A CSAT scheme as provided herein may offer several advantages for mixedRAT co-existence, particular in unlicensed spectrum. For example, byadapting communication based on signals associated with a first RAT(e.g., Wi-Fi), a second RAT (e.g., LTE) may react to utilization of aco-channel by devices that use the first RAT while refraining fromreacting to extraneous interference by other devices (e.g., non-Wi-Fidevices) or adjacent channels. As another example, a CSAT scheme enablesa device that uses one RAT to control how much protection is to beafforded to co-channel communications by devices that use another RAT byadjusting the particular parameters employed. In addition, such a schememay be generally implemented without changes to the underlying RATcommunication protocol. In an LTE system, for example, CSAT may begenerally implemented without changing the LTE PHY or MAC layerprotocols, but by simply changing the LTE software.

To improve overall system efficiency, the CSAT cycle may besynchronized, in whole or in part, across different small cells, atleast within a given operator. For example, the operator may set aminimum CSAT ON (activated) period (T_(ON,min)) and a minimum CSAT OFF(deactivated) period (T_(OFF,min)). Accordingly, the CSAT ON (activated)period durations and transmission powers may be different, but minimumdeactivation times and certain channel selection measurement gaps may besynchronized.

FIG. 8 is a flow diagram illustrating an example method of CSATparameter adaptation for reducing interference between RATs. The methodmay be performed, for example, in whole or in part, by a small cell basestation (e.g., the small cell base station 110C illustrated in FIG. 1)and/or by a user device (e.g., the user device 120C illustrated in FIG.1).

As shown, the method 800 may include receiving signals via a resourceusing a first (e.g., Wi-Fi) RAT (block 810). The resource may include orotherwise correspond to, for example, an unlicensed radio frequency bandshared by Wi-Fi and LTE devices. To better associate received signalingwith the first RAT and distinguish it from other RAT signaling as wellas noise, a particular transceiver operating in accordance with thefirst RAT may be used to receive the signals (rather than a transceiveroperating in accordance with another RAT that scans for aggregatebackground signal strength). The term “transceiver” as used herein mayrefer to different types of transmission and/or reception components,and is not intended to imply that such components are necessarilycapable of both transmission and reception. As discussed above, such atransceiver may include a fully-functioning transmission/reception radioor a lower functionality receiver circuit, and may be co-located withanother transceiver operating in accordance with another RAT.

The small cell base station and/or user device may then identify autilization of the resource that is associated with the first RAT basedon the received signals (block 820). Utilization of the resource maygive an indication of an amount of interference (e.g., co-channelinterference) that is associated with first RAT signaling. Based on theidentified utilization of the resource, one or more cycling parametersmay be set for a TDM communication pattern defining CSAT ON (activated)and CSAT OFF (deactivated) periods of transmission for a second (e.g.,LTE) RAT sharing the resource (block 830), and operation of the secondRAT may be cycled between CSAT ON (activated) and CSAT OFF (deactivated)periods of transmission over the resource in accordance with the TDMcommunication pattern (block 840). As discussed above, the CSAT OFF(deactivated) periods provide not only opportunities for the first RATto use the resource but also opportunities to measure first RATsignaling.

Measurements may be conducted on the resource and the resource may becharacterized in terms of its utilization in various ways. For example,for a shared Wi-Fi medium, a co-located Wi-Fi radio may sniff the mediumfor Wi-Fi packets. Wi-Fi packets may be detected by decoding one or moreWi-Fi signatures. Examples of such signatures include Wi-Fi preambles,Wi-Fi PHY headers, Wi-Fi MAC headers, Wi-Fi beacons, Wi-Fi proberequests, Wi-Fi probe responses, and so on. The co-located Wi-Fi radiomay then extract various characteristics of the detected Wi-Fi packets.Example characteristics include packet duration, signal strength orenergy (e.g., RSSI), traffic type (e.g., high vs. low QoS), Wi-Fichannel type (e.g., primary vs. secondary), and other attributes of thepackets related to the impact on or need to prioritize Wi-Fi signaling.The utilization of the Wi-Fi medium may be determined based on theextracted (e.g., decoded) characteristics of the of the detected Wi-Fipackets.

Returning to FIG. 8, setting the cycling parameters (block 830) maycomprise changing at least one of the cycling parameters based on acomparison of the identified utilization of the resource with athreshold. For example, a medium utilization metric for the first RAT(MU_(RAT1)) may be calculated as a function of the duration D of eachdetected packet, such that MU_(RAT1)=ΣD_(i)/T_(M), where iεψ. Here, ψ isthe set of detected packets of the first RAT that have an RSSI above acorresponding level (e.g., −62 dBm) and T_(M) is a normalization factorbased on the length of the measurement or observation period (e.g., theT_(OFF) duration for a CSAT OFF (deactivated) period in whichmeasurements are performed). Packets that having a relatively low RSSImay be filtered out of the medium utilization calculation because of thelimited impact that operation of the second RAT is likely to have onthose packets.

The utilization metric MU_(RAT1) may be compared to a corresponding setof utilization thresholds (TH_(UTIL)) associated with a level ofprotection to be afforded to the first RAT. That is, the utilizationthreshold(s) TH_(UTIL) may be set (statically or dynamically) to controlthe amount of protection afforded to the first RAT. For example, ifinspection of the detected packets indicates that the packets require ahigh Quality of Service (QoS) from the first RAT, the utilizationthreshold(s) TH_(UTIL) may be adjusted downward to increase sensitivityto operation by the first RAT. Conversely, if inspection of the detectedpackets indicates that the packets do not require a high QoS, theutilization threshold(s) TH_(UTIL) may be adjusted upward to decreasesensitivity to operation by the first RAT.

Various cycling parameters may be set or changed as desired. Forexample, as discussed in more detail above with respect to FIG. 7, theCSAT cycling parameters may include or otherwise correspond to a dutycycle, a transmit power, cycle timing (e.g., the start/stop time of eachCSAT cycle), and so on. Each parameter may be bounded by correspondingmax (e.g., T_(OFF,max)) and min (e.g., T_(OFF,min)) values asappropriate for a given system, and modifications to the cyclingparameters may be constrained by a hysteresis parameter (H) to limitundue state oscillations.

As an example, the CSAT OFF (deactivated) period may be increased by astep ΔT (up to, at most, a specified maximum) if the utilization of theresource MU_(RAT1) by the first RAT exceeds a threshold utilizationTH_(UTIL) value, or decreased by a step ΔT (down to, at most, aspecified minimum) if the utilization of the resource MU_(RAT1) fallsbelow a threshold utilization TH_(UTIL) value.

An example algorithm is as follows:

CSAT OFF = min (T_(OFF,max); CSAT OFF + ΔT) if MU_(RAT1) > TH_(UTIL),CSAT OFF = max (T_(OFF,min); CSAT OFF − ΔT) if MU_(RAT1) < TH_(UTIL) −H, else CSAT OFF = CSAT OFF.

Accordingly, it will be appreciated that any of the above parameters maybe set or adjusted to control how a resource is utilized by competingRATs, based on how much protection is to be provided for one of theRATs.

Returning to FIG. 8, in some designs, the cycling parameters may befurther set or modified based on characteristics of the second RATitself (optional block 850). For example, the small cell base station oruser device may determine that there is a traffic or backhaul limitationassociated with the second RAT, and modify the cycling parameters basedon the determined limitation. If the traffic buffer for the second RATdrops below some threshold for a relatively long time, this may be takenas an indication that the second RAT does not have a high need for theresource at the moment, and steps may be taken to reduce the secondRAT's usage of the medium (e.g., by decreasing the CSAT ON (activated)period, increasing the CSAT OFF (deactivated) period, increasing theT_(OFF,max) restriction, and so on). Similar steps may be taken ifbackhaul limitations restrict the extent to which the second RAT mayutilize the resource.

As another example, if the second RAT requires a high QoS on theresource, steps may be taken to increase the second RAT's usage of theresource (e.g., by increasing the CSAT ON (activated) period, decreasingthe CSAT OFF (deactivated) period, decreasing the T_(OFF,max)restriction, and so on). Conversely, if the second RAT does not requirea high QoS on the resource, steps may be taken to decrease the secondRAT's usage of the resource (e.g., by decreasing the CSAT ON (activated)period, increasing the CSAT OFF (deactivated) period, increasing theT_(OFF,max) restriction, and so on).

In some instances, the cycling parameters may be further modifiedopportunistically, on a more short-term basis, to address as needed anytemporary issues that may arise.

FIG. 9 illustrates an example opportunistic modification of a CSATcommunication scheme to accommodate pending retransmissions. As in FIG.7, during CSAT ON (activated) periods of communication, transmission ona resource such as an unlicensed band is enabled. During CSAT OFF(deactivated) periods, transmission on the resource is disabled to allowother-system operations and to conduct measurements.

As shown in FIG. 9, in some designs, a given CSAT ON (activated) periodmay be opportunistically extended. For example, the small cell basestation may determine that a retransmission procedure (e.g., HARQ)associated with communication on the resource by the second RAT is stillpending at or near the edge of a CSAT ON (activated) period. Inresponse, the small cell base station may extend the CSAT ON (activated)period for the second RAT on the resource in order to complete theretransmission procedure. To reduce the usage of this extended CSAT ON(activated) period by other second RAT traffic, however, the small cellbase station may stop scheduling (or assigning) new DL grants as the endof the CSAT ON (activated) period approaches.

In some instances, additional operations may be performed over the firstRAT to effectuate coordination with the CSAT scheme being employed.

FIG. 10 illustrates an example of inter-RAT coordination utilizing aClear-to-Send-to-Self (CTS2S) message. As in FIG. 7, during CSAT ON(activated) periods of communication, transmission on a resource such asan unlicensed band is enabled. During CSAT OFF (deactivated) periods,transmission on the resource is disabled to allow other-systemoperations and to conduct measurements.

As shown in FIG. 10, in some designs, a co-located transceiver operatingaccording to the first (e.g., Wi-Fi) RAT may be used to transmit a CTS2Smessage on the resource to reserve the resource for a transmission bythe second RAT. The CTS2S message may be transmitted before the end of aCSAT OFF (deactivated) period to reserve the resource for the second RATduring the next CSAT ON (activated) period. The CTS2S message mayinclude a duration indication corresponding to the duration of theupcoming CSAT ON (activated) period. The CTS2S message transmissionpower may be adapted to control its range, as desired (and, hence, thenumber of affected first RAT devices).

In some instances, the cycling parameter setting and adaptationoperations described above may be split between a small cell basestation (e.g., the small cell base station 110C illustrated in FIG. 1)and one or more user devices (e.g., the user device 120C illustrated inFIG. 1), with various layers of coordination.

FIGS. 11-12 are signaling flow diagrams illustrating different examplesof split processing and message exchanges between a small cell basestation and a user device for coordinating CSAT operation. By way ofexample, the small cell base station is shown as the small cell basestation 110C illustrated in FIG. 1 and the user device is shown as theuser device 120C illustrated in FIG. 1.

In the example of FIG. 11, the user device performs signalingmeasurements of a shared resource using a first (e.g., Wi-Fi) RAT (block1102). The user device then transmits a message 1104 to the small cellbase station that includes measurement information indicative of theutilization of the resource. The measurement information may include themeasurements themselves or a further processed version thereof,including a utilization metric of the type described above. Based on themeasurement information, the small cell base station may determine oneor more CSAT cycling parameters (block 1106). The small cell basestation then transmits a response message 1108 to the user device thatincludes the determined cycling parameters.

In the example of FIG. 12, the user device similarly performs signalingmeasurements of a shared resource using a first (e.g., Wi-Fi) RAT (block1202). In contrast to the example of FIG. 11, however, the user deviceitself determines one or more recommended CSAT cycling parameters basedon the measurement information (block 1204). The user device thentransmits a message 1206 to the small cell base station that includesthe recommended CSAT cycling parameters. In response, the small cellbase station may make a determination concerning the recommended CSATcycling parameters (block 1208) and transmit a response message 1210 tothe user device that includes an acknowledgement confirming therecommended CSAT cycling parameters, or some form of negativeacknowledgement or notification of alternative parameters.

Accordingly, in each of these examples, the user device may transmit amessage to the small cell base station that is based on the utilizationof the resource and receive a response message that includes (e.g.,directly or indirectly via confirmation) one or more cycling parameters.The various message content and corresponding processing operations,however, may vary. In either case, the small cell base station maysynchronize (e.g., via the cycling parameters in the response message)cycling of uplink operation of the second RAT by the user device andcycling of downlink operation of the second RAT by the small cell basestation. For example, the uplink TDM communication pattern may beselected as a subset of the downlink TDM communication pattern so thatuplink communications are only permitted during periods in which thesmall cell base station is active.

In practice, turning a given RAT such as LTE off during certain periodsmay impact other operations of the communication system. For example, auser device may attempt to perform various measurements during a CSATOFF (deactivated) period, such as Carrier-to-Interference (C/I),Reference Signal Received Power (RSRP), Reference Signal ReceivedQuality (RSRQ), and Channel Quality Indicator (CQI) measurements, butwill not be able to find the corresponding base station during this timesince the base station is not transmitting. This may impact measurementand timing accuracy, tracking loop procedures, cell reselectionprocedures, etc., and detrimentally affect proper operation of thesystem. Accordingly, in some designs, the small cell base station can beconfigured to ignore certain information reported by the user devicesfor CSAT OFF (deactivated) periods.

Returning again to FIG. 7, the illustrated TDM communication pattern maybe applied to not just one frequency (e.g., SCell) but to severaldifferent frequencies on which the small cell base station providescommunication services. In some instances, the same TDM communicationpattern may be applied to all of the different frequencies. However, inother instances, it may be advantageous to apply a different TDMcommunication pattern to the different frequencies.

Applying different TDM communication patterns to different frequenciesmay provide flexibility and certain associated advantages. However, CSAToperation across different frequencies and different TDM communicationpatterns may be impeded by and/or require coordination with otheroperations of the communication system, such as Discontinuous Deception(DRX).

FIG. 13 illustrates an example DRX communication mode, which may be usedto communicate with certain user devices (illustrated at LTE UEs) forapplications that do not require continuous reception. DRX is generallyadvantageous in that it allows user devices to conserve battery power bymonitoring control channels only at configurable or predeterminedintervals rather than continuously.

As shown, during certain predetermined or negotiated times, the userdevice's receiver (RX) is turned ON (e.g., in a connected state), whileat other times, it is turned OFF (referred to as a DRX gap) and the userdevice enters a low power state. During the ON duration of a given DRXcycle, the user device's receiver may monitor a corresponding PhysicalDownlink Control Channel (PDCCH) or the like to identify DL data. Thebase station serving the user device may control or otherwise be awareof the DRX operation, and schedule communications accordingly.

As is further illustrated in FIG. 13, it may be advantageous to alignthe DRX pattern with the CSAT TDM communication pattern, at least to acertain extent and for certain user devices. For example, the basestation may align the DRX pattern of one or more high-traffic userdevices (e.g., a user device served in the 5 GHz band, which isgenerally associated with high traffic) with the CSAT TDM communicationpattern to maximize or at least increase the overlap between the DRX ONperiod and the CSAT ON (activated) period, thereby increasingtransmission opportunities and overall throughput for the user devices.

In conventional DRX implementations, however, a single DRX pattern isconfigured (e.g., through RRC signaling) for each user device across allof its different frequencies (SCells). This conventional implementationprevents simultaneous alignment of DRX with different CSAT TDMcommunication patterns.

FIG. 14 illustrates an example DRX broadcast/multicast message forconfiguring user devices in accordance with various DRX parameters, asan alternative to conventional RRC signaling. In this example, thebroadcast/multicast message 1400 is illustrated as a System InformationBlock (SIB) which may be transmitted by a small cell base station on itsPCell to all user devices being served. The broadcast/multicast message1400 carries respective DRX parameters for each SCell (SCell1, SCell2, .. . , SCellN). The broadcast/multicast message 1400 is accordingly ableto specify individual DRX configurations that are different acrossSCells but common to all user devices. This is in contrast toconventional, user-specific (unicast) RRC messages, which specify DRXconfigurations that are specific to each user device but common to allSCells on which that user device operates. By utilizing such abroadcast/multicast message, the base station may establish differentCSAT TDM communication patterns on different SCells while at the sametime configuring DRX to align with each of the different CSAT TDMcommunication patterns.

FIG. 15 is a flow diagram illustrating an example method of coordinatingDRX configurations across user devices in a wireless communicationsystem. The method may be performed, for example, by a small cell basestation (e.g., the small cell base station 110C illustrated in FIG. 1).

As shown, the method 1500 includes the small cell base station assigningdifferent DRX configurations for different communication channels (e.g.,SCells) (block 1510). The small cell base station may then transmit(e.g., broadcast or multicast) a DRX configuration message to aplurality of user devices specifying one or more DRX parameters for eachof the different DRX configurations (block 1520). Communication thenproceeds via the communication channels, where for each of thecommunication channels, the communication uses a corresponding one ofthe DRX configurations (block 1530).

As discussed in more detail above, the DRX configuration message may bebroadcasted on a licensed frequency band PCell for different unlicensedfrequency band SCells providing the different communication channels. Asan example, the DRX configuration message may be broadcasted in a SIB.The specified DRX parameters may include, for example, a DRX gap, a dutycycle, cycle timing, or a combination thereof.

As further discussed in more detail above, the DRX configuration messagemay be used to coordinate DRX with different CSAT cycling parameters(optional block 1540). As an example, one or more cycling parameters maybe set for a first TDM communication pattern defining CSAT ON(activated) and CSAT OFF (deactivated) periods of transmission on afirst one of the communication channels such that the first TDMcommunication pattern is aligned with the corresponding DRXconfiguration of the first one of the communication channels. Similarly,one or more cycling parameters may be set for a second TDM communicationpattern (different from the first TDM communication pattern) definingCSAT ON (activated) and CSAT OFF (deactivated) periods of transmissionon a second one of the communication channels such that the second TDMcommunication pattern is aligned with the corresponding DRXconfiguration of the second one of the communication channels. Operationmay then be cycled between CSAT ON (activated) and CSAT OFF(deactivated) periods of transmission on the first one and second one ofthe communication channels in accordance with the first and second TDMcommunication patterns.

To maintain the DRX and CSAT coordination, the small cell base stationmay monitor (e.g., continuously, periodically, or on an event-drivenbasis) for changes in the CSAT communication scheme and dynamicallyadjust the DRX configurations, as needed, based on (directly orindirectly) the same underlying inter-RAT utilization of the sharedresource invoking CSAT (optional block 1550). For example, the smallcell base station may receive signals via the resource using a first(e.g., Wi-Fi) RAT, whereas the first one and second one of thecommunication channels share the resource but are associated with asecond (e.g., LTE) RAT. The resource may include or otherwise correspondto, for example, an unlicensed radio frequency band shared by Wi-Fi andLTE devices, as discussed above. The small cell base station may thenidentify a utilization of the resource that is associated with the firstRAT based on the received signals (block 1520). Utilization of theresource may give an indication of an amount of interference (e.g.,co-channel interference) that is associated with first RAT signaling.

Based on the identified utilization of the resource, the small cell basestation may adjust the first and second TDM communication patterns andadjust the corresponding DRX configurations to align with the adjustedfirst and second TDM communication patterns. The adjusted DRXconfigurations may then be transmitted to the plurality of user devices,using the DRX configuration message provided herein.

Returning again to FIG. 7 and the discussion above, other advantagesthat may be provided by applying different TDM communication patterns todifferent frequencies include improved management of higher QoS traffic.For example, relatively long CSAT OFF (deactivated) periods (e.g., onthe order of hundreds of msec) on any given frequency (e.g., SCell) mayintroduce latencies that are detrimental to some applications, includinghigh QoS real-time or near real-time communications such asVoice-Over-IP (VOIP). One approach to combating this is to speciallyadapt the TDM communication patterns to protect latency sensitiveapplications, such as by using a tighter CSAT cycle (i.e., shorter CSATON (activated)/CSAT OFF (deactivated) period durations), as discussedabove. Alternatively or in addition, however, the TDM communicationpatterns may also be staggered in time across the different frequencieswith respect to an overlap in their CSAT ON (activated)/CSAT OFF(deactivated) periods, such that user traffic on a particular frequencythat is deactivated for a given period may be switched over to another,activated frequency for service during that time period. The staggeringof TDM communication patterns may be employed across differentfrequencies for downlink CSAT communication (e.g., transmission by thesmall cell base station) as well as for uplink CSAT communication (e.g.,transmission by a user device).

FIG. 16 illustrates an example CSAT communication scheme utilizingstaggered TDM communication patterns across different frequencies. Inthis example, two frequencies (provided as SCell1 and SCell2) are shownfor illustration purposes. Their respective TDM communication patternsare staggered in time with respect to an overlap in their CSAT ON(activated) and CSAT OFF (deactivated) periods, such that the small cellbase station (e.g., via its scheduler) may use at least one frequencyfor communication over a shared resource at any given time.

FIG. 17 illustrates another example CSAT communication scheme utilizingstaggered TDM communication patterns across different frequencies. Inthis example, three frequencies (provided as SCell1, SCell2, and SCell3)are shown for illustration purposes. Their respective TDM communicationpatterns are again staggered in time with respect to an overlap in theirCSAT ON (activated) and CSAT OFF (deactivated) periods, such that thesmall cell base station (e.g., via its scheduler) may use at least onefrequency for communication over a shared resource at any given time.

FIG. 18 is a flow diagram illustrating an example method of CSATcommunication employing staggered TDM communication patterns. The methodmay be performed, for example, in whole or in part, by a small cell basestation (e.g., the small cell base station 110C illustrated in FIG. 1)and/or by a user device (e.g., the user device 120C illustrated in FIG.1).

As shown, the method 1800 includes receiving signals via a resourceusing a first (e.g., Wi-Fi) RAT (block 1810). The resource may includeor otherwise correspond to, for example, an unlicensed radio frequencyband shared by Wi-Fi and LTE devices. The small cell base station and/oruser device may then identify a utilization of the resource that isassociated with the first RAT based on the received signals (block1820). Utilization of the resource may give an indication of an amountof interference (e.g., co-channel interference) that is associated withfirst RAT signaling.

Based on the identified utilization of the resource, cycling parametersmay be set for different TDM communication patterns defining respectiveCSAT ON (activated) and CSAT OFF (deactivated) periods of transmissionfor different frequencies (SCells) of a second (e.g., LTE) RAT sharingthe resource (block 1830). For example, one or more cycling parametersmay be set for a first TDM communication pattern on a first frequencyand one or more cycling parameters may be set for a second TDMcommunication pattern on a second frequency, with the first TDMcommunication pattern and the second TDM communication pattern beingstaggered in time with respect to an overlap in their CSAT ON(activated) and CSAT OFF (deactivated) periods. In particular, the firstTDM communication pattern and the second TDM communication pattern maybe staggered in time such that the CSAT ON (activated) periods of thefirst TDM communication pattern correspond to the CSAT OFF (deactivated)periods of the second TDM communication pattern, and the CSAT OFF(deactivated) periods of the first TDM communication pattern correspondto the CSAT ON (activated) periods of the second TDM communicationpattern.

Operation of the second RAT may then be cycled between CSAT ON(activated) and CSAT OFF (deactivated) periods of transmission over theresource on the different frequencies in accordance with theirrespective TDM communication patterns (block 1840). When necessary orotherwise appropriate (e.g., for high-QoS applications), data trafficmay be scheduled to hop over the different frequencies in accordancewith the different TDM communication patterns in order to maintain amore constant and lower latency transmission stream (optional block1850). In particular, returning to the example above, data traffic maybe transmitted on the first frequency during a CSAT ON (activated)period of the first TDM communication pattern and transmitted on thesecond frequency during a CSAT OFF (deactivated) period of the first TDMcommunication pattern (i.e., corresponding to a CSAT ON (activated)period of the second TDM communication pattern). As discussed above,such a staggered arrangement among the TDM communication patternscorresponding to different frequencies allows data traffic to be steeredtowards and scheduled on an appropriate active connection at any giventime.

Although CSAT communication may be used for co-existing with native RATssuch as Wi-Fi (or other RATs or network operators) on differentunlicensed frequencies and corresponding channels as discussed above,the interference impact to the native RAT may be different on thosedifferent channels. For example, the IEEE 802.11 protocol family ofstandards provides operation for a primary 20 MHz channel as well asoptionally using secondary adjacent channels (e.g., extension channels)spaced ±20 MHz away for channel bonding and to increase Wi-Fi bandwidthto, for example, 40 MHz, 80 MHz, or 160 MHz. In the scenario where aWi-Fi AP is using channel bonding of two 20 MHz channels to form a 40MHz channel, or four 20 MHz channels to form an 80 MHz channel, and soon, one of the 20 MHz channels will be specified as a primary channeland the rest of the channels as secondary channels. Because primarychannels are used by Wi-Fi APs to send beacons, high QoS traffic, andfor connection setup exchanges (e.g., association and authentication),the impact of interference on a primary channel may be more substantialthan on secondary channels.

Accordingly, channel selection (e.g., via the CHS algorithm 610) may befurther configured to prefer operation on secondary channels as opposedto primary channels (if no clean channel is found). In either case,whether a primary or secondary channel is selected, a CSAT communicationscheme may be implemented on the selected channel in accordance with thetechniques provided herein to afford additional protection to the nativeRAT. If operation on a primary channel is necessary (e.g., if no cleanor even secondary channels are found), the corresponding TDMcommunication pattern can be specially adapted to protect primarychannel operation (e.g., using shorter CSAT ON (activation)/CSAT OFF(deactivation) period durations, using TDM communication patterns thatminimize the overlap of LTE transmissions with Wi-Fi beacons, etc.). Thesmall cell base station can classify which channels are primary orsecondary through detecting a Wi-Fi beacon signal, for example, whichmay be sent on the primary channel, and also through reading the contentof the Wi-Fi beacon signal, which may contain information identifyingthe primary channel and secondary channels used by the Wi-Fi AP. Similartechniques may be applied to other RATs as well when different channelsprovide different operations for the RAT.

FIG. 19 is a flow diagram illustrating an example method of channelselection among a plurality of channels. The method may be performed,for example, by a small cell base station (e.g., the small cell basestation 110C illustrated in FIG. 1).

As shown, the method 1900 may include receiving signals via a resourceusing a first (e.g., Wi-Fi) RAT (block 1910). The resource may includeor otherwise correspond to, for example, an unlicensed radio frequencyband shared by Wi-Fi and LTE devices. The small cell base station maythen identify a utilization of the resource that is associated with thefirst RAT based on the received signals (block 1920). Utilization of theresource may give an indication of an amount of interference (e.g.,co-channel interference) that is associated with first RAT signaling.

Based on the identified utilization of the resource, the small cell basestation may select an unlicensed frequency for communication over theresource by a second (e.g. LTE) RAT (block 1940). For example, if theidentified utilization of the resource is relatively clean (e.g., belowa clean channel threshold) on a first frequency, the small cell basestation may select that frequency for communication over the resource bythe second RAT. However, if the identified utilization of the resourceis not clean (e.g., above the clean channel threshold) on any of theplurality of frequencies available as a candidate, the small cell basestation may select a second frequency for communication over theresource by the second RAT. In particular, a frequency associated with asecondary channel of the first RAT may be selected as the secondfrequency if one or more secondary channels are identified as operatingon the resource, whereas a frequency associated with a primary channelof the first RAT may be selected as the second frequency if no secondarychannels are identified as operating on the resource.

As discussed above, when necessary, the first RAT channels operating onthe resource may be classified as primary or secondary in a variety ofways (optional block 1930). For example, the small cell base station maydecode a beacon signal among the received signals and use the beaconsignal (e.g., by mere header detection or by reading its contents) toidentify if any secondary channels are operating on the resource.However, in other scenarios, the small cell base station may alreadyhave knowledge (e.g., via pre-provisioning or prior decoding operations)of which channel classes for the first RAT correspond to whichfrequencies in a shared frequency band.

In either case, when there is no clean channel available, the small cellbase station may implement a CSAT communication scheme on the selected(second) frequency and set a TDM communication pattern defining CSAT ON(activated) and CSAT OFF (deactivated) periods of transmission on thesecond frequency over the resource by the second RAT (optional block1950). While any of the TDM communication pattern adaptation techniquesdescribed above may be employed, when the frequency associated with theprimary channel of the first RAT is selected as the (second) frequency,the TDM communication pattern may be further adapted to protect primarychannel operation. For example, the TDM communication pattern may be setto use relatively short (e.g., below a threshold) CSAT ON (activated)and CSAT OFF (deactivated) period durations to reduce interference toconnection setup signaling of the first RAT on the primary channel. Asanother example, the TDM communication pattern may be set to minimizeoverlap of the CSAT ON (activated) periods with beacon signaling of thefirst RAT on the primary channel.

Communications on the selected (second) frequency may also in someinstances be sent at a lower power level in response to the frequencyassociated with the primary channel of the first RAT being selected asthe second frequency, as compared to the frequency associated with thesecondary channel of the first RAT being selected as the secondfrequency. This reduced transmission power may provide furtherprotections for primary channel operation by the first RAT.

FIG. 20 illustrates several sample components (represented bycorresponding blocks) that may be incorporated into an apparatus 2002,an apparatus 2004, and an apparatus 2006 (corresponding to, for example,a user device, a base station, and a network entity, respectively) tosupport the CSAT and related operations as taught herein. It will beappreciated that these components may be implemented in different typesof apparatuses in different implementations (e.g., in an ASIC, in anSoC, etc.). The illustrated components may also be incorporated intoother apparatuses in a communication system. For example, otherapparatuses in a system may include components similar to thosedescribed to provide similar functionality. Also, a given apparatus maycontain one or more of the components. For example, an apparatus mayinclude multiple transceiver components that enable the apparatus tooperate on multiple carriers and/or communicate via differenttechnologies.

The apparatus 2002 and the apparatus 2004 each include at least onewireless communication device (represented by the communication devices2008 and 2014 (and the communication device 2020 if the apparatus 2004is a relay)) for communicating with other nodes via at least onedesignated RAT. Each communication device 2008 includes at least onetransmitter (represented by the transmitter 2010) for transmitting andencoding signals (e.g., messages, indications, information, and so on)and at least one receiver (represented by the receiver 2012) forreceiving and decoding signals (e.g., messages, indications,information, pilots, and so on). Similarly, each communication device2014 includes at least one transmitter (represented by the transmitter2016) for transmitting signals (e.g., messages, indications,information, pilots, and so on) and at least one receiver (representedby the receiver 2018) for receiving signals (e.g., messages,indications, information, and so on). If the apparatus 2004 is a relaystation, each communication device 2020 may include at least onetransmitter (represented by the transmitter 2022) for transmittingsignals (e.g., messages, indications, information, pilots, and so on)and at least one receiver (represented by the receiver 2024) forreceiving signals (e.g., messages, indications, information, and so on).

A transmitter and a receiver may comprise an integrated device (e.g.,embodied as a transmitter circuit and a receiver circuit of a singlecommunication device) in some implementations, may comprise a separatetransmitter device and a separate receiver device in someimplementations, or may be embodied in other ways in otherimplementations. A wireless communication device (e.g., one of multiplewireless communication devices) of the apparatus 2004 may also comprisea Network Listen Module (NLM) or the like for performing variousmeasurements.

The apparatus 2006 (and the apparatus 2004 if it is not a relay station)includes at least one communication device (represented by thecommunication device 2026 and, optionally, 2020) for communicating withother nodes. For example, the communication device 2026 may comprise anetwork interface that is configured to communicate with one or morenetwork entities via a wire-based or wireless backhaul. In some aspects,the communication device 2026 may be implemented as a transceiverconfigured to support wire-based or wireless signal communication. Thiscommunication may involve, for example, sending and receiving: messages,parameters, or other types of information. Accordingly, in the exampleof FIG. 20, the communication device 2026 is shown as comprising atransmitter 2028 and a receiver 2030. Similarly, if the apparatus 2004is not a relay station, the communication device 2020 may comprise anetwork interface that is configured to communicate with one or morenetwork entities via a wire-based or wireless backhaul. As with thecommunication device 2026, the communication device 2020 is shown ascomprising a transmitter 2022 and a receiver 2024.

The apparatuses 2002, 2004, and 2006 also include other components thatmay be used in conjunction with the CSAT and related operations astaught herein. The apparatus 2002 includes a processing system 2032 forproviding functionality relating to, for example, user device operationsto support CSAT and related aspects as taught herein and for providingother processing functionality. The apparatus 2004 includes a processingsystem 2034 for providing functionality relating to, for example, basestation operations to support CSAT and related aspects as taught hereinand for providing other processing functionality. The apparatus 2006includes a processing system 2036 for providing functionality relatingto, for example, network operations to support CSAT and related aspectsas taught herein and for providing other processing functionality. Theapparatuses 2002, 2004, and 2006 include memory components 2038, 2040,and 2042 (e.g., each including a memory device), respectively, formaintaining information (e.g., information indicative of reservedresources, thresholds, parameters, and so on). In addition, theapparatuses 2002, 2004, and 2006 include user interface devices 2044,2046, and 2048, respectively, for providing indications (e.g., audibleand/or visual indications) to a user and/or for receiving user input(e.g., upon user actuation of a sensing device such a keypad, a touchscreen, a microphone, and so on).

For convenience, the apparatuses 2002, 2004, and/or 2006 are shown inFIG. 20 as including various components that may be configured accordingto the various examples described herein. It will be appreciated,however, that the illustrated blocks may have different functionality indifferent designs.

The components of FIG. 20 may be implemented in various ways. In someimplementations, the components of FIG. 20 may be implemented in one ormore circuits such as, for example, one or more processors and/or one ormore ASICs (which may include one or more processors). Here, eachcircuit may use and/or incorporate at least one memory component forstoring information or executable code used by the circuit to providethis functionality. For example, some or all of the functionalityrepresented by blocks 2008, 2032, 2038, and 2044 may be implemented byprocessor and memory component(s) of the apparatus 2002 (e.g., byexecution of appropriate code and/or by appropriate configuration ofprocessor components). Similarly, some or all of the functionalityrepresented by blocks 2014, 2020, 2034, 2040, and 2046 may beimplemented by processor and memory component(s) of the apparatus 2004(e.g., by execution of appropriate code and/or by appropriateconfiguration of processor components). Also, some or all of thefunctionality represented by blocks 2026, 2036, 2042, and 2048 may beimplemented by processor and memory component(s) of the apparatus 2006(e.g., by execution of appropriate code and/or by appropriateconfiguration of processor components).

FIG. 21 illustrates an example base station or user device apparatus2100 represented as a series of interrelated functional modules. Amodule for receiving 2102 may correspond at least in some aspects to,for example, a communication device as discussed herein. A module foridentifying 2104 may correspond at least in some aspects to, forexample, a processing system as discussed herein. A module for setting2106 may correspond at least in some aspects to, for example, aprocessing system as discussed herein. A module for cycling 2108 maycorrespond at least in some aspects to, for example, a processing systemin conjunction with a communication device as discussed herein.

FIG. 22 illustrates an example base station apparatus 2200 representedas a series of interrelated functional modules. A module for assigning2202 may correspond at least in some aspects to, for example, aprocessing system as discussed herein. A module for transmitting 2204may correspond at least in some aspects to, for example, a communicationdevice as discussed herein. A module for communicating 2206 maycorrespond at least in some aspects to, for example, a communicationdevice as discussed herein.

FIG. 23 illustrates an example base station or user device apparatus2300 represented as a series of interrelated functional modules. Amodule for receiving 2302 may correspond at least in some aspects to,for example, a communication device as discussed herein. A module foridentifying 2304 may correspond at least in some aspects to, forexample, a processing system as discussed herein. A module for setting2306 may correspond at least in some aspects to, for example, aprocessing system as discussed herein. A module for setting 2308 maycorrespond at least in some aspects to, for example, a processing systemas discussed herein. A module for cycling 2310 may correspond at leastin some aspects to, for example, a processing system in conjunction witha communication device as discussed herein.

FIG. 24 illustrates an example base station apparatus 2400 representedas a series of interrelated functional modules. A module for receiving2402 may correspond at least in some aspects to, for example, acommunication device as discussed herein. A module for identifying 2404may correspond at least in some aspects to, for example, a processingsystem as discussed herein. A module for selecting 2406 may correspondat least in some aspects to, for example, a processing system asdiscussed herein. A module for selecting 2408 may correspond at least insome aspects to, for example, a processing system as discussed herein.

The functionality of the modules of FIGS. 21-24 may be implemented invarious ways consistent with the teachings herein. In some designs, thefunctionality of these modules may be implemented as one or moreelectrical components. In some designs, the functionality of theseblocks may be implemented as a processing system including one or moreprocessor components. In some designs, the functionality of thesemodules may be implemented using, for example, at least a portion of oneor more integrated circuits (e.g., an ASIC). As discussed herein, anintegrated circuit may include a processor, software, other relatedcomponents, or some combination thereof. Thus, the functionality ofdifferent modules may be implemented, for example, as different subsetsof an integrated circuit, as different subsets of a set of softwaremodules, or a combination thereof. Also, it will be appreciated that agiven subset (e.g., of an integrated circuit and/or of a set of softwaremodules) may provide at least a portion of the functionality for morethan one module.

In addition, the components and functions represented by FIGS. 21-24, aswell as other components and functions described herein, may beimplemented using any suitable means. Such means also may beimplemented, at least in part, using corresponding structure as taughtherein. For example, the components described above in conjunction withthe “module for” components of FIGS. 21-24 also may correspond tosimilarly designated “means for” functionality. Thus, in some aspectsone or more of such means may be implemented using one or more ofprocessor components, integrated circuits, or other suitable structureas taught herein.

FIG. 25 illustrates an example communication system environment in whichthe CSAT and related operation teachings and structures herein may bemay be incorporated. The wireless communication system 2500, which willbe described at least in part as an LTE network for illustrationpurposes, includes a number of eNBs 2510 and other network entities.Each of the eNBs 2510 provides communication coverage for a particulargeographic area, such as macro cell or small cell coverage areas.

In the illustrated example, the eNBs 2510A, 2510B, and 2510C are macrocell eNBs for the macro cells 2502A, 2502B, and 2502C, respectively. Themacro cells 2502A, 2502B, and 2502C may cover a relatively largegeographic area (e.g., several kilometers in radius) and may allowunrestricted access by UEs with service subscription. The eNB 2510X is aparticular small cell eNB referred to as a pico cell eNB for the picocell 2502X. The pico cell 2502X may cover a relatively small geographicarea and may allow unrestricted access by UEs with service subscription.The eNBs 2510Y and 2510Z are particular small cells referred to as femtocell eNBs for the femto cells 2502Y and 2502Z, respectively. The femtocells 2502Y and 2502Z may cover a relatively small geographic area(e.g., a home) and may allow unrestricted access by UEs (e.g., whenoperated in an open access mode) or restricted access by UEs havingassociation with the femto cell (e.g., UEs in a Closed Subscriber Group(CSG), UEs for users in the home, etc.), as discussed in more detailbelow.

The wireless network 2500 also includes a relay station 2510R. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., an eNB or a UE) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE or an eNB). A relay station may also be a UE thatrelays transmissions for other UEs (e.g., a mobile hotspot). In theexample shown in FIG. 25, the relay station 2510R communicates with theeNB 2510A and a UE 2520R in order to facilitate communication betweenthe eNB 2510A and the UE 2520R. A relay station may also be referred toas a relay eNB, a relay, etc.

The wireless network 2500 is a heterogeneous network in that it includeseNBs of different types, including macro eNBs, pico eNBs, femto eNBs,relays, etc. As discussed in more detail above, these different types ofeNBs may have different transmit power levels, different coverage areas,and different impacts on interference in the wireless network 2500. Forexample, macro eNBs may have a relatively high transmit power levelwhereas pico eNBs, femto eNBs, and relays may have a lower transmitpower level (e.g., by a relative margin, such as a 10 dBm difference ormore).

Returning to FIG. 25, the wireless network 2500 may support synchronousor asynchronous operation. For synchronous operation, the eNBs may havesimilar frame timing, and transmissions from different eNBs may beapproximately aligned in time. For asynchronous operation, the eNBs mayhave different frame timing, and transmissions from different eNBs maynot be aligned in time. Unless otherwise noted, the techniques describedherein may be used for both synchronous and asynchronous operation.

A network controller 2530 may couple to a set of eNBs and providecoordination and control for these eNBs. The network controller 2530 maycommunicate with the eNBs 2510 via a backhaul. The eNBs 2510 may alsocommunicate with one another, e.g., directly or indirectly via awireless or wireline backhaul.

As shown, the UEs 2520 may be dispersed throughout the wireless network2500, and each UE may be stationary or mobile, corresponding to, forexample, a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,or other mobile entities. In FIG. 25, a solid line with double arrowsindicates desired transmissions between a UE and a serving eNB, which isan eNB designated to serve the UE on the downlink and/or uplink. Adashed line with double arrows indicates potentially interferingtransmissions between a UE and an eNB. For example, UE 2520Y may be inproximity to femto eNBs 2510Y, 2510Z. Uplink transmissions from UE 2520Ymay interfere with femto eNBs 2510Y, 2510Z. Uplink transmissions from UE2520Y may jam femto eNBs 2510Y, 2510Z and degrade the quality ofreception of other uplink signals to femto eNBs 2510Y, 2510Z.

Small cell eNBs such as the pico cell eNB 2510X and femto eNBs 2510Y,2510Z may be configured to support different types of access modes. Forexample, in an open access mode, a small cell eNB may allow any UE toobtain any type of service via the small cell. In a restricted (orclosed) access mode, a small cell may only allow authorized UEs toobtain service via the small cell. For example, a small cell eNB mayonly allow UEs (e.g., so called home UEs) belonging to a certainsubscriber group (e.g., a CSG) to obtain service via the small cell. Ina hybrid access mode, alien UEs (e.g., non-home UEs, non-CSG UEs) may begiven limited access to the small cell. For example, a macro UE thatdoes not belong to a small cell's CSG may be allowed to access the smallcell only if sufficient resources are available for all home UEscurrently being served by the small cell.

By way of example, femto eNB 2510Y may be an open-access femto eNB withno restricted associations to UEs. The femto eNB 2510Z may be a highertransmission power eNB initially deployed to provide coverage to anarea. Femto eNB 2510Z may be deployed to cover a large service area.Meanwhile, femto eNB 2510Y may be a lower transmission power eNBdeployed later than femto eNB 2510Z to provide coverage for a hotspotarea (e.g., a sports arena or stadium) for loading traffic from eitheror both eNB 2510C, eNB 2510Z.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations may be used herein as a convenient method of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements may be employed there or that the first element must precedethe second element in some manner. Also, unless stated otherwise a setof elements may comprise one or more elements. In addition, terminologyof the form “at least one of A, B, or C” or “one or more of A, B, or C”or “at least one of the group consisting of A, B, and C” used in thedescription or the claims means “A or B or C or any combination of theseelements.” For example, this terminology may include A, or B, or C, or Aand B, or A and C, or A and B and C, or 2A, or 2B, or 2C, and so on.

In view of the descriptions and explanations above, those of skill inthe art will appreciate that the various illustrative logical blocks,modules, circuits, and algorithm steps described in connection with theaspects disclosed herein may be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

Accordingly, it will be appreciated, for example, that an apparatus orany component of an apparatus may be configured to (or made operable toor adapted to) provide functionality as taught herein. This may beachieved, for example: by manufacturing (e.g., fabricating) theapparatus or component so that it will provide the functionality; byprogramming the apparatus or component so that it will provide thefunctionality; or through the use of some other suitable implementationtechnique. As one example, an integrated circuit may be fabricated toprovide the requisite functionality. As another example, an integratedcircuit may be fabricated to support the requisite functionality andthen configured (e.g., via programming) to provide the requisitefunctionality. As yet another example, a processor circuit may executecode to provide the requisite functionality.

Moreover, the methods, sequences, and/or algorithms described inconnection with the aspects disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module may reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage mediumknown in the art. An exemplary storage medium is coupled to theprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium may be integral to the processor (e.g., cache memory).

Accordingly, it will also be appreciated, for example, that certainaspects of the disclosure can include a computer-readable mediumembodying a method for CSAT and related operations.

While the foregoing disclosure shows various illustrative aspects, itshould be noted that various changes and modifications may be made tothe illustrated examples without departing from the scope defined by theappended claims. The present disclosure is not intended to be limited tothe specifically illustrated examples alone. For example, unlessotherwise noted, the functions, steps, and/or actions of the methodclaims in accordance with the aspects of the disclosure described hereinneed not be performed in any particular order. Furthermore, althoughcertain aspects may be described or claimed in the singular, the pluralis contemplated unless limitation to the singular is explicitly stated.

What is claimed is:
 1. A method of Carrier Sense Adaptive Transmission(CSAT) for reducing interference between Radio Access Technologies(RATs), comprising: receiving signals via a resource, wherein a firsttransceiver operating in accordance with a first RAT is used to receivethe signals; identifying a utilization of the resource that isassociated with the first RAT, wherein the identification is based onthe received signals; setting one or more cycling parameters of a TimeDivision Multiplexing (TDM) communication pattern defining activated anddeactivated periods of transmission for a second RAT sharing theresource, wherein the setting is based on the identified utilization ofthe resource; and cycling operation of the second RAT between activatedand deactivated periods of transmission over the resource in accordancewith the TDM communication pattern.
 2. The method of claim 1, whereinthe resource is an unlicensed radio frequency band.
 3. The method ofclaim 1, wherein: the first RAT comprises Wi-Fi technology; and thesecond RAT comprises Long Term Evolution (LTE) technology.
 4. The methodof claim 1, wherein: a second transceiver operating in accordance withthe second RAT performs transmission over the resource during theactivated periods of the TDM communication pattern; and the firsttransceiver and the second transceiver are co-located.
 5. The method ofclaim 1, wherein identifying the utilization of the resource comprisesdetermining at least one of: a transmission duration associated with apacket of the first RAT, a received signal strength associated with apacket of the first RAT, or a combination thereof.
 6. The method ofclaim 5, wherein the determining comprises decoding at least one of: apreamble, a Physical (PHY) header, a Medium Access Control (MAC) header,a beacon, a probe request, a probe response, or a combination thereof.7. The method of claim 1, further comprising: requesting that ameasurement be conducted on the resource during a deactivated period ofthe TDM communication pattern, wherein the measurement is for thesignals received using the first transceiver operating in accordancewith the first RAT.
 8. The method of claim 1, wherein the settingcomprises changing at least one of the one or more cycling parametersbased on a comparison of the identified utilization of the resource witha threshold associated with a level of protection afforded to the firstRAT.
 9. The method of claim 8, further comprising: determining a Qualityof Service (QoS) associated with the first RAT based on the receivedsignals; and adjusting the threshold based on the determined QoS. 10.The method of claim 1, wherein the one or more cycling parameterscomprise at least one of: a duty cycle, a transmit power, cycle timing,or a combination thereof.
 11. The method of claim 1, further comprising:determining a traffic or backhaul limitation associated with the secondRAT, wherein the setting is further based on the determined limitation.12. The method of claim 1, further comprising: determining a Quality ofService (QoS) requirement associated with the second RAT, wherein thesetting is further based on the determined requirement.
 13. The methodof claim 1, further comprising: determining that a retransmissionprocedure is pending, wherein the retransmission procedure is associatedwith communication on the resource by the second RAT; and extending anactivated period of the TDM communication pattern for the second RAT onthe resource in response to the determination.
 14. The method of claim1, further comprising transmitting a Clear-to-Send-to-Self (CTS2S)message on the resource via the first RAT to reserve the resource for atransmission by the second RAT.
 15. The method of claim 1, wherein atleast one of the receiving, identifying, setting, cycling, or acombination thereof is performed by a small cell base station.
 16. Themethod of claim 1, wherein at least one of the receiving, identifying,setting, cycling, or a combination thereof is performed by a userdevice.
 17. The method of claim 16, further comprising: transmitting amessage from the user device to a small cell base station, wherein themessage is based on the utilization of the resource; and receiving aresponse message at the user device from the small cell base station,wherein the response message is received in response to the transmittedmessage and comprises at least one of the one or more cyclingparameters.
 18. The method of claim 17, wherein: the message transmittedto the small cell base station comprises measurement informationindicative of the utilization of the resource; and the response messagereceived from the small cell base station comprises a cycling parameterdetermined by the small cell base station based on the measurementinformation.
 19. The method of claim 17, wherein: the messagetransmitted to the small cell base station comprises a recommendedcycling parameter determined by the user device based on the identifiedutilization of the resource; and the response message received from thesmall cell base station comprises a confirmation of the recommendedcycling parameter.
 20. The method of claim 17, wherein the at least oneof the one or more cycling parameters received in the response messagefrom the small cell base station synchronizes (i) cycling of uplinkoperation of the second RAT by the user device and (ii) cycling ofdownlink operation of the second RAT by the small cell base station. 21.An apparatus for Carrier Sense Adaptive Transmission (CSAT) for reducinginterference between Radio Access Technologies (RATs), comprising: afirst transceiver configured to receive signals via a resource, whereinthe first transceiver operates in accordance with a first RAT to receivethe signals; a processor configured to: identify a utilization of theresource that is associated with the first RAT, wherein theidentification is based on the received signals, set one or more cyclingparameters of a Time Division Multiplexing (TDM) communication patterndefining activated and deactivated periods of transmission for a secondRAT sharing the resource, wherein the setting is based on the identifiedutilization of the resource, and control cycling of operation of thesecond RAT between activated and deactivated periods of transmissionover the resource in accordance with the TDM communication pattern; andmemory coupled to the processor for storing related data andinstructions.
 22. A method of coordinating Discontinuous Reception (DRX)configurations across user devices in a wireless communication system,comprising: assigning different DRX configurations for differentcommunication channels; transmitting a DRX configuration message to aplurality of user devices specifying one or more DRX parameters for eachof the different DRX configurations; and communicating via thecommunication channels, wherein for each of the communication channels,the communication uses a corresponding one of the DRX configurations.23. The method of claim 22, wherein the transmitting comprisesbroadcasting or multicasting the DRX configuration message on a licensedfrequency band Primary Cell (PCell) for different unlicensed frequencyband Secondary Cells (SCells) providing the different communicationchannels.
 24. The method of claim 22, wherein the transmitting comprisesbroadcasting or multicasting the DRX configuration message in a SystemInformation Block (SIB).
 25. The method of claim 22, wherein the DRXparameters comprise at least one of: a DRX gap, a duty cycle, cycletiming, or a combination thereof.
 26. The method of claim 22, furthercomprising: setting one or more cycling parameters of a first TimeDivision Multiplexing (TDM) communication pattern defining activated anddeactivated periods of transmission on a first one of the communicationchannels, wherein the first TDM communication pattern is aligned withthe corresponding DRX configuration of the first one of thecommunication channels; setting one or more cycling parameters of asecond TDM communication pattern defining activated and deactivatedperiods of transmission on a second one of the communication channels,wherein the second TDM communication pattern is different from the firstTDM communication pattern and aligned with the corresponding DRXconfiguration of the second one of the communication channels; andcycling operation between activated and deactivated periods oftransmission on the first one and second one of the communicationchannels in accordance with the first and second TDM communicationpatterns.
 27. The method of claim 26, further comprising: receivingsignals via a resource, wherein a first Radio Access Technology (RAT) isused to receive the signals; and identifying a utilization of theresource that is associated with the first RAT, wherein theidentification is based on the received signals, wherein the first oneand second one of the communication channels share the resource and arecommunicated over the resource via a second RAT.
 28. The method of claim27, further comprising: adjusting the first and second TDM communicationpatterns based on the identified utilization of the resource; adjustingthe corresponding DRX configurations of the first one and second one ofthe communication channels to align with the adjusted first and secondTDM communication patterns; and transmitting the adjusted DRXconfigurations to the plurality of user devices.
 29. The method of claim27, wherein: the resource is an unlicensed radio frequency band; thefirst RAT comprises Wi-Fi technology; and the second RAT comprises LongTerm Evolution (LTE) technology.
 30. An apparatus for coordinatingDiscontinuous Reception (DRX) configurations across user devices in awireless communication system, comprising: a processor configured toassign different DRX configurations for different communicationchannels; a first transceiver configured to: transmit a DRXconfiguration message to a plurality of user devices specifying one ormore DRX parameters for each of the different DRX configurations, andcommunicate via the communication channels, wherein for each of thecommunication channels, the communication uses a corresponding one ofthe DRX configurations; and memory coupled to the processor for storingrelated data and instructions.